Process for glazing earthenware and glaze therefor



Patented Feb. 28, 1950 PEGCESS FOR GRAZING EAETHENWARE AND GLAZE THEREFOR Aymon Francois Max Claudet, Orly, France, assignor to Societe des. Usines Chirniqucs Rhone- Poulenc, Paris, France, a body corporate of France No Drawing. Application August 20, 1946, Serial No. 691,886. In France May 11, 1944 Section 1, Eublic Law 690, August 8, 19% Patent expires May 11, 1964 Claims.

This invention is for improvements in or relating to enamels or glazes for earthenware.

There have been numerousproposals for solving the problem of preparing enamels without boron or lead for temperaturesv of application between 1000 and 1100? C., but these glazes, generally rich in alkalies, had the disadvantage of crazing on the usual earthenware clays, although in certain cases this drawback could be overcome by replacing Nazo by K20. However, up to the present, no enamels free from boron and lead have been found for the important common earthenware and pottery industry, of which the firing temperatures are between 900 and 980 C.

It has now been found that the firing temperature of enamels and earthenware coatings free from boron and lead can be reduced to 850 C. According to the present invention, this result can be obtained by means of compositions which contain, in addition to the usual constituents of glazes (silica, alumina, alkaline oxides, zinc oxide), also the oxidesof titanium and barium; the chief effect of the simultaneous presence of these latter oxides is the lowering of the glazing temperature considerably below the limits known heretofore.

Another advantage which accrues from this invention is that the quantity of alkaline oxides can baconsiderably reducedin comparison with the boronand lead-free compositions already known. In consequence, it is possible to overcome effiorescence and, on the usual clays, the crazing inevitably produced with very alkaline glazes.

The new glazes obtained according to the presend invention have, moreover, the advantage of exhibiting high resistance to acids, and in particular culinary acids, the corrosive action of which on the usual enamels is well known.

The following molecular compositions are illustrative of glazes of the present invention:

1st composition.-Earthenware coating glazing at 850 to 950 CL 0.38 NazO 0.13 K20 83.} 0.1 A1203 0.04 CaO 0.20 Ba0 2 2nd compositiom-Earthenware coating for 1000 to 1100 C.

- 0.33 NazO I 0.12 K 0 5 .g'i f 0.22 A1203 0.05 CaO 1 2 0.20 BaO' 0.30 ZnO The mixture of raw materials ordinarily utilised for the preparation of frits is fused at about 1250 C. and poured into water. The frit is ground to the usual fineness in the presence of water with any desired additions, applied to the ceramic support and fired at a temperature between 850 and 950 C. for composition (1) and between 1000 and 1100" C. for composition (2). In both cases, a very brilliant glaze is obtained which fully satisfies requirements.

Based on the foregoing examples, it will be perceived that the range of percentage of ingredients of the coating is as follows:

Per cent S102 61.4-64.3 TiOz 2.4-2.9 A1203 3.7-6.7 NazO 9.4 12.0 C210 0.3 132.0 9.0-11..1 ZnO 7.2-7.3

I claim: 1. Process of producing glazed earthenware which consists in applying to a ceramic support a frit of the following molecular composition:

' {0.38 NazO 0.13 K20 a 2 0.1 A1203 2 0.20 BaO 0.25 ZnO and firing the coated support at a temperature of 850 to 950 C.

2. Process of producing glazed earthenware which consists in applying to a ceramic support a frit of the following molecular composition:

0.33 NazO 0.12 K20 9 0.22 A1203 0.05 CaO 0.10 T102 0.20 BaO 0.30 ZnO and firing the coated support at a temperature of 1000 to 1100 C.

3. A glaze for earthenware of the followin molecular composition:

0.38 NazO 0.13 K20 3:3 @18 0.1 A1203 0.04 CaO 2 0.20 BaO 0.25 ZnO 4. A glaze for earthenware of the following molecular composition:

0.33 N220 0.12 K20 g'g fgg 0.22 A1203 0.05 CaO 0.20 BaO 0.30 ZnO 5. Process for producing glazed earthenware which consists in applying to a ceramic support a frit of the following weight percentage composition:

Per cent SiOz 61.4-64.3 TiOz 2.4-2.9 1131206 3.7-6.7

K20 24-120 CaO 0.8

Bao 9.0-11.1

ZnO 7.2-7.3

6. A glaze for earthenware of the following weight percentage composition:

Per cent SiOz 61.4-64.3 T102 2.4-2.9 A1203 3.7-6.7 NazO 9.4-1.2.9 CaO 0.8 B20 9.0-11.1

ZnO 7.2-7.3

AYMON FRANCOIS MAX CLAUDET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER, REFERENCES American Ceramic Society Transactions VII (1900). 

5. PROCESS FOR PRODUCING GLAZED EARTHENWARE WHICH CONSISTS IN APPLYING TO A CERAMIC SUPPORT A FRIT OF THE FOLLOWING WEIGHT PERCENTAGE COMPOSITION: 